Fan arrangement for domestic appliances



Feb. 17, 1959 J. H. POWERS 2, 73

FAN ARRANGEMENT FOR DOMESTIC APPLIANCES Filed Feb. 21, 1955 I 3Sheets-Sheet 1 IN V EN TOR.

d AM ES H POWERS H S ATTORN EY Feb. 17, 1959 J. H. POWERS FANARRANGEMENT FOR DOMESTIC APPLIANCES Filed Feb. 21, 1955 3 Sheets-Sheet 2m m 0 O O STAT C PRESSU E o w. o M. M.

sTAT C DQESSUQE CFM INVEN TOR.

JAMES H. POWERS HIS ATTORNEY Feb. 17, 1959 J. H. POWERS. 2,873,908

FAN ARRANGEMENT FOR DOMESTIC APPLIANCES JAMES H. POWERS M HIS ATTORNEYUnited States Patent FAN ARRANGEMENT FOR DOMESTIC APPLIANCES James H.Powers, Anchorage, Ky., assignor to General Electric Company, acorporation of New York Application February 21, 1955, Serial No.489,483

2 Claims. (Cl. 230-119) My invention relates to fan arrangements, andmore particularly to such arrangements for moving air through an elementwhich resists the flow of air, and to domestic appliances using such fanarrangements.

Air moving means such as propeller fans or blowers are provided invarious types of domestic appliances in order to create a flow of airtherethrough. For example, room air conditioners, dehumidifiers, and airpurifying or filtering appliances all include fans or blowers forsetting up a flow of air over their air treating means. In a room airconditioner one fan or blower is utilized to send a stream of room airthrough a filter and over a refrigerant evaporator, and a second fan orblower is used to force a stream of outside air over a refrigerantcondenser. In a dehumidifier a fan or blower is utilized to send astream of room air over an evaporator, and in an air purifying applianceone of these air moving means is used to force a flow of air through afilter or purifying element.

Which of them, a propeller fan or a blower, is used in any particularappliance depends upon the application.

The conventional axial flow propeller fan delivers a large volume of airthrough a air treating means when no appreciable static pressure isrequired in order to create the flow, that is, when it is operatingsubstantially as a free air fan. But if the air treating means offersany substantial resistance to air flow, the propeller fan is notsuitable because the fiow from the fan drops oif considerably as theresistance increases, and in fact if the air treating means presentsagreat enough resistance to flow, the fan may not send any air through itat all. This is because, in the operation of a propeller fanapproximately 75% of the air moved is thrown forwardly from the tips ofthe blades, the remaining 25% being thrust forwardly from the centralarea of the fan. In other words the center of the fan is weak; and as aresult, if a sufficient resistance is encountered in the output forwardflow, the air takes the path of least resistance and flows back throughthe center of the fan to the rear intake side thereof, from which areait again is thrust forwardly by the tips of the blades. In this way, alocal recirculation of the air occurs in a closed path right through thecenter of the fan. Due to this return and recirculation the fan isunable to build sufficient pressure to force the air through theresistance.

A centrifugal blower on the other hand creates a comparatively largestatic pressure so that it can force air through air treating means ofrelatively high resistance. But in operation, the blower packs airagainst the air treating means or other resistance by centrifugalpressure, and in doing so creates a vortex within the center of theblower wheel; this vortex limits the volume of flow by causing the airto tend to thin out in the center of the wheel with the result that theoutput flow is restricted. This phenomenon is commonly known as shockloss. Thus, while a blower may be used to deliver a given volume of airthrough a resistance, a comparatively large, powerful and expensive oneis required.

Because of these characteristics, a propeller fan is Patented Feb. 17,1959 ordinarily used where a large volume of air is to be delivered andno great pressure is required whereas the blower is used when the needfor pressure is the overriding factor. In the above-mentioned domesticappliances it is ordinarily the air treating means which presents themajor portion of the resistance to air flow, and it is thus therequirements of the air treating means which have determined which fanwill be used, a propellertype fan or a blower-type fan. Wheneverpossible, it has been customary to use a propeller fan since such fansare less expensive than blowers and occupy less space. But in certaininstances, for example when the air flow is to pass through highresistance mechanical or electrostatic filters or through relativelythick heat exchangers, it has been necessary to use blowers despitetheir greater cost and space requirement. Thus blowers are oftenemployed both in air purifying appliances and in room air conditionersin order to obtain the desired flow. The resulting appliances andconditioners have therefore, of course, been more expensive and bulkierthan if fans could have been used.

Accordingly, it is an object of my invention to provide a new andimproved fan arrangement by which an axial flow propeller fan is enabledto pass an air stream through high resistance air treating elements.

It is another object of my invention to provide a new and improved fanarrangement having materially different and improved pressure and volumecharacteristics than those obtained from conventional free air axialflow propeller fans.

A further object of my invention is to provide a new and improved fanarrangement which enables an axial flow propeller fan to produce higherpressures than heretofore possible with such fans and also to maintainsubstantial flow .at such higher pressures.

Still another object of my invention is to provide a fan arrangement ofthe above type having new and improved means for shaping andaccelerating the output flow.

My invention also has as its object the provision of a new and improvedair purifying appliance utilizing an axial flow propeller fan forcreating the air flow therethrough.

In carrying out my invention I provide a fan arrangement utilizing agenerally axial flow fan having a plurality of air propelling blades. Inthis arrangement the intake opening to the fan is defined by an annularshroud, and the shroud is so mounted that it surrounds at least the rearportion of the fan. By my invention the arrangement further includesmeans for efiecting a pressure rise in the output flow from the fan.These means comprise a panel positioned directly in front of the outputside of the fan for diverting radially the output flow therefrom, and achamber surrounding the forward portion of the fan and the shroud andcontaining a body of free air for collecting therein the radial floweffected by the panel. This chamber has side walls spaced substantiallyequidistant from the fan; and as the output flow of the fan passes intothe chamber, a pressure rise is etfected in the flow. As I understandit, this pressure. rise is due both to centrifugal forces set up as aresult of the radial outward and circular movement of the flow, and to afree stream diffusion process occurring as the flow passes through thearea between the panel and the shroud. Because of its change to theradial direction, the flow is directed away from the center of the fanand prevented from return and re-circulation therethrough. After it hasincreased in pressure, the flow is then discharged from the chamber bymeans of an outlet opening leading therefrom outwardly of the peripheryof the blades and the shroud, By reason of the pressure rise so effectedin the output flow, this arrangement enables the axial flow fan tomaintain flow through high resistance air treating means or to be usedin other applications where a relatively high pressure is required.

The novel features which I believe to be characteristic of my inventionare set forth with particularityin the appended claims. My inventionitself, however, both as to its organization and method of operation maybe best understood by reference to the following description taken inconjunction with the accompanying drawings in which:

Fig. 1 is a vertical sectional view of an improved air purifyingappliance incorporating a preferred embodiment of my new and improvedfan arrangement as a part thereof;

Fig. 2 is a vertical sectional view taken on the line 2-2 of Fig. 1;

Fig. 3 is a graph showing the performance characteristics of the fanarrangement of Fig. l for different spacings between the fan and thefront panel;

Fig. 4 is a graph showing the performance characteristics of the fanarrangement of Fig. 1 for different spacings between the fan and thesides of the collecting chamber;

Fig. 5 is a schematic view in vertical section of an improved airpurifier incorporating an alternate embodiment of my fan arrangement;

Fig. 6 is a schematic view in vertical section of an air purifierincluding another embodiment of my new and improved fan arrangement;

Fig. 7 is a schematic view in vertical section of an air purifierincluding still another embodiment of my fan arrangement;

Fig. 8 is a front view of the air purifier of Fig. 7;

Fig. 9 is a fragmentary schematic view in vertical section of an airpurifier embodying an additional feature of my invention, this purifierincluding novel means for accelerating and shaping the output flow fromthe purifier;

and

Fig. 10 is a fragmentary top view of the air purifier of Fig. 9.

Referring now to Figs. 1 and 2, I have shown therein an air purifying orfiltering appliance 1 which incorporates a preferred embodiment of mynew and improved fan arrangement. The purifier 1 includes ahousing 2 towhich an air inlet opening is provided by a grill 3 at the rear thereof.This grill extends completely across the back of the appliance from topto bottom and from side to side and, as shown, is designed with inclinedthe dust particles or other materials are given a negative charge asthey pass the side 6 of the filter. Then as the air stream carries themto side 5 of the filter these particles or other materials are attractedby the high potential side 5 and held on the elements thereof. In otherwords, the high potential side of the filter acts to pull the particlesout of the air and thereby filter it. Further, the filter 4 includesporous or gauze-like sheets of material which are positioned between theelectrically charged sides 5 and 6 and which also help to filter theair. The gauze-like sheets of material act as simple mechanical filtersto catch and retain dust or other passageway so that it is impossiblefor a child to stick his fingers or other articles through itspassageways. It should be understood, however, that any suitable grillmay be used and that a grill with inclined passageways,

- such as is illustrated, is not necessary to the operation of myinvention.

Within the housing 2 and directly in front of the grill 3 thereispositioned a filter element 4. Like the grill 3 the filter element 4extends completely across the housing 2 and thus any air flowing throughthe grill 3 and into .the housing 2 must necessarily pass through thefilter element 4. This filter element 4 is of the electrostatic type andincludes a high potential side 5 and a negative or grounded side 6. Thehigh potential side 5 is energized by means of a spring-biased contact 7which is connected to a high voltage source or power pack 8. The powerpack includes a step-up transformer and a rectifier, and the applianceis provided with a cord (not shown) so that the power pack may beenergized from any con ventional household electrical outlet. Theopposite or negative side 6 of the filter is likewise engaged by aspring contact, and this contact 9 is connected directly to the housing2 so that the negative side 6 is always grounded.

The negative side 6 of the filter 4 lies adjacent to the extraneousmaterials in the air entering the purifier 1,

particles.

In order that the filter element 4 may be removed from the housing forcleaning purposes or to be replaced, it is mounted on a separate housingsection 10 which is releasably attached to the rest of the housing. Thehousing section 10 may be attached to the bottom wall of the housing byany suitable means as for example by clips, and when these clips orother means are released, the housing section 10 and the filter 4 may bepulled completely out of the housing. Suitable safety means (not' shown)are provided so that Whenever the filter is taken out of the housing thesupply circuit to the power pack. 8 is broken and it isde-energized.Further, on chance that there may be some charge remaining in the powerpack even though the supply circuit is broken, the contact 7 is soarranged that it automatically rotates downwardly and comes into contactwith the housing 2 as the filter is removed. This effectively groundsthe power pack and insures that there is no stray voltage remaining toinjure anyone.

To create a fiow of air through the filter element 4 I have mountedwithin the housing 1a preferred embodiment of my new and improved fanarrangement. This fan arrangement utilizes a generally axial fiow,propeller fan 11. The fan 11 includes a plurality of blades 12, and isdriven by an electric motor 13 through a shaft 14. Both the fan 11 andthe motor 13 are supported by means of mounting brackets 15 which areattached to the casing of the motor 13 at their one end and to thebottom plate 16 of the housing 2 at their other ends. It will beunderstood however that any suitable means may be utilized to mount themotor and the fan within the housing.

To define an intake opening to the fan 11 there is provided an annularshroud or ring 17. This shroud extends forwardly from the rear or intakeside of the fan sothat it surrounds at least a portion of the peripheryof the blades. Specifically in my preferred embodiment it extendsforwardly so that it surrounds two-thirds of the fan from rear to front,that is, two-thirds of the projected thickness of the fan bladesmeasured from the rear. Only the front one-third of the fan extendsoutwardly beyond the front edge 18 of the shroud. I have found that thebest results are produced by arranging the shroud in this manner so thatit surrounds the rear twothirds of the fan with the forward one-third ofthe fan extending outwardly from it.

As is better shown in Fig. 2 the annular shroud 17 at its rear edge'isattached to or is formed integrally with a panel or wall 19. This panel19 extends outwardly from the rear edge of the shroud to all sides ofthe housing 2, and it completely isolates the space within the housingbehind the fan from the space within the housing in front of the fan.Due to the panel 19 the only way air can pass from the space behind thefan to the space in front of the fan is through the fan itself. In mypreferred embodiment the lower and middle portions of the panel 19extend outwardly in generally the same plane as the rear of the fan,that is, the plane containing the rear edges of the blades, to thebottom wall 16 of the housing and to the side walls 20 and 21 of thehousing. However, the portion of panel 19 above centrifugal effect.

the shroud is slanted rearwardly toward the filter 4 as it extendsupwardly to the top wall 22 of the housing.

In my novel fan arrangement, now to be described, the fan 11 is soarranged that it is effective to produce a greater pressure than isnormally obtainable from axial free air flow fans. More exactly, the fan11 is so arranged that it produces a greater pressure than it itselfcould produce if utilized in the customary arrangements for axial airflow fans. This higher pressure is needed in order to pull the airthrough the filter element 4 which presents a relatively high resistanceto the flow of air particularly when clogged up after use.

In the embodiment of Figs. 1 and 2, my novel fan arrangement includes apanel or planar baffle 23 which is positioned directly in front of theoutput side of the fan so that the axially moving output stream of thefan flows directly into it. Preferably, this panel 23 comprises thefront wall of the air purifier housing 2. The panel 23 serves to divertradially outward the axial output flow of the fan, or in other words itchanges the direction of the output flow of the fan as soon as it leavesthe fan. In addition to the panel 23 my fan arrangement also includes achamber which contains a body of free air for collecting the radial floweffected by the panel. This collecting chamber in accordance with myinvention extends around or surrounds at least the forward portions ofthe fan 11 and its shroud 17. For example, in the embodiment of Figs. 1and 2 a chamber 24 surrounding the fan 11 and the shroud 17 is definedby the front wall or panel 23, the shroud 17 itself, the panel 19extending outwardly from the shroud, the side walls 20 and 21 of thehousing and the bottom wall 16 of the housing. Actually, the chamber 24so defined by these walls, surrounds more than just the forward portionsof the fan and the shroud; it in fact surrounds substantially all of theshroud and the fan and thereby provides a body of free air all aroundthem. However, as mentioned above, the chamber may surround only theforward or output portions of the fan and the shroud and my increasedpressure and volume effect now to be explained will still be produced.But for best results the chamber should use the fan shroud as the rearwall thereof so that the full depth of shroud is included in thechamber. I have found that the combination of apanel positioned directlyin front of an axial flow fan, and a chamber surrounding at least theforward portions of the fan and its shroud for collecting the radialflow effected by the panel, is effective to cause a pressure rise in theoutput flow from the fan. In other words, the conversion of the axialoutput flow to radial flow by the panel 23 and the collection of .thisradial flow by the body of free air contained in the chamber 24 causes apressure rise in the flow itself. As-I understand this novel pressurerise, it occurs because my fan arrangement in effect converts the axialflow fan into a mixed flow compressor by adding 3. Normally an axialflow fan, such as the fan 11, when operating as a free air fan, addsenergy to the air by increasing its kinetic energy with only a'verysmall rise in pressure. However, by restricting the axial output flowwith a plate or panel, such as the panel 23, the output air is made moreto flow out radially. As a result, a centrifugal force field is createdin the fan output flow and a pressure rise is experienced due to thecentrifugal forces on adjacent air molecules in the centrifugal forcefield. In addition to this effect, a pressure rise also occurs in theregion of the annular peripheral area lying between the forward end 18of the shroud and the panel 23. In other words an additional pressurerise occurs at the area of the radial discharge between the shroud andthe panel. This pressure rise results from a free stream diffusionprocess which is simply a conversion of some of the radial velocity headleaving the blades into a pressure head by virtue of a decrease in thevelocity of the moving air. Moreover, because of the change in thedirection of flow directly in front of the 6 fan, the increased pressureis not lost through leakage at the center of the fan. The flow beingdirected radially away from the fan is prevented from returning andrecirculating through its' center. Thus .there is no substantial leakageflow to diminish and/or limit the pressure otherwise produced by thefan.

To explain the pressure rise in somewhat simpler language it may also bedescn'fbed as follows: One pressure rise is effected by the decrease invelocity of the axial air flow from the fan as it is converted to radialflow by the interference of the panel; and a second pressure rise iseffected by the decrease in velocity of the radial flow as itscentrifugal forces are resisted by the adjacent free air in the exhaustor collecting chamber. Further, because the flow is directed away fromthe center of the fan, there is effectively no leakage therethrough todiminish and/or limit the pressure. But whatever the explanation may be,I have found by actual tests that a material pressure rise is effectedin the output flow of the fan by my novel fan arrangement.

It will be noted incidentally that the bottom corners of the chamberformed by the plane, parallel side walls 20 and 21 and the bottom wall16 are right-angle or square corners. These square corners provide adamping action on any whirling circulation which may tend .to occur inthe body of free air contained in the chamber 24; and I have found thatbetter results from the standpoint of pressure increase and air flow areobtained from my fan arrangement when such damping of the 'body of freeair is employed. When the body of air within the chamber 24 is heldrelatively still, higher pressures are produced than when the body offree air is able'to cin culate freely. It will be understood though thatmy invention is not limited to a chamber with square corners sincechambers with rounded corners and a more freely circulating body of airmay be used although with not quite so good results. Whatever thechamber configuration, sound deadening material may be placed on'thewalls to reduce noise without materially affecting the pressure andvolume characteristics obtained.

After a pressure rise has been effected in the output flow from the fanby means of my new and improved arrangement, the flow is then dischargedoutwardly from the chamber. In order to provide means for this discharge flow, an outlet opening is defined in the chamber 24 outwardly ofthe periphery of the blades 12 of the fan. Specifically in theembodiment of Figs. 1 and 2 the outlet opening comprises an aperture 25in the top wall 22 of the housing. This aperture or opening 2 5 iscovered with a perforate grill 25a for safety purposes. Although theoutput flow from the fan flows radially in all directions along thepanel 23 into the chamber 24, the flow eventually works its way aroundand goes out through the opening 25. In fact, the outlet opening wouldnot have to be in the topwall of the chamber, rather it could be in anywall thereof, outwardly of the periphery of the fan blades, and the flowwould still find its way to it. My increased pressure effect would beobtained just as in the embodiment of Figs. 1 and 2 provided that theopening were positioned outwardly of the periphery of the blades. Itwill be noted that in the embodiment of Figs. 1 and 2, because of theinclination of the wall 19, the chamber 24 widens out from front to rearjust be low the outlet opening 25. This widening of the chamber howeveris not necessary to this embodiment and could be eliminated if desired.

In the embodiment shown in Figs. 1 and 2 the fan 11 is of coursepulling" air through a filter mounted on the downstream side of the fanrather than forcing air through a filter mounted on the upstream side ofthe fan. In order to pull through the filter, the fan 11 creates apartial vacuum in the portion of the housing lying on the downstreamside of the filter but on the upstream side of the fan. In other wordsit creates a partial vacuum in the portion of the housing generallyindicated at 26.

This partial vacuum in the space 26 then allows the normal atmosphericpressure to force air through the filter 4 into that space. The amountof flow through the filter of course depends upon the magnitude of thepartial vacuum created by the fan.

My new and improved fan arrangement enables the fan 11 to create ahigher vacuum in the space 26 than would have been heretofore possiblewith an axial fan. The fan 11 during its operation pulls the air out ofthe space 26 and throws it outwardly toward the panel 23. As explainedabove, a pressure rise then occurs in the air flow as it moves into thechamber 24. By the time the flow is absorbed by the free air in thechamber 24 it has risen to a pressure slightly higher than atmospheric.Because of this slightly higher pressure the air then moves outwardlythrough the openings 25 into the surrounding atmosphere. Since thepressure of the output flow is only slightly more than atmospheric atthe opening 25 and can rise no higher, and since a large pressure riseoccurs between the output of the fan and the opening 25, this means thatthe pressure immediately in front of the fan is much lower thanatmospheric. Further, since a small rise is experienced as the airpasses through the fan itself, the pressure in the chamber 26 is evenlower. The increased pressure effect resulting from my novel arrangementis added to the normal pressure effect of the fan to cause a lowering ofthe pressure in the chamber 26 to a point much below that which would bepossible with the fan mounted in the conventional manner to operate infree air. As a result the fan 11 is enabled to maintain a satisfactoryflow through the filter 4 even when it clogs up with use.

In order to explain more fully the results which may be obtained by theuse of my new and improved fan arrangement, I have shown in Figs. 3 and4 a set of performance curves showing variations in air delivered incubic feet per minute (C. F. M.) with variations in static pressure ininches of mercury for a ten inch, 23 pitch, axial fiow propeller typefan mounted as shown in Figs. 1 and 2, each curve being for a differentspacing between the fan and the front panel 23 or between the fan andthe side walls of the collecting chamber. For the purpose of comparison,Figs. 3 and 4 also include a curve showing the performance of the fanwhen mounted in the conventional manner to operate as a free air fanwithout any obstruction to the free flow of air discharged from it. Thefan employed to obtain the data from which these curves were plotted isof a standard propeller type and was driven by a 1/50 horsepower motorat approximately 1550 revolutions per minute.

Referring to Fig. 3 the curve 27 indicates the normal results which areproduced by this ten inch fan when it is operated as a free air fan inthe customary manner to discharge freely straight out into theatmosphere. It will be noted that the maximum pressure which may beproduced with the fan operating in this conventional manner isapproximately 0.22 inch of mercury measured immediately in front of thefan, and at this pressure the flow from the fan is practicallynegligible. The curves 28, 29, and 30, however, indicate the resultswhich are obtained when my new and improved fan arrangement is used. Asthese curves show, my fan arrangement enables the fan to produce muchhigher pressures, for example over 0.5 inches of mercury, and tomaintain substantial flow at these higher presures.

The curves 28, 29 and 30 were plotted from data obtained by using a fanarrangement in which the side walls 20 and 21 of the collecting chamber24 were fixed and positioned 4 inches from the periphery of the fan, andthe bottom wall 16 also fixed, was positioned 2 inches from the fanperiphery; but the fan and the shroud were .moved together as a unitrelative to the diverting plate or panel 23 so as to vary the distancetherebetween. The positions of the fan and the shroud relative to eachother were, however, kept the same. For the curve 28 the dis tancebetween the forward end 18 of the panel and the shroud was 1% inches,for the curve 29 the distance was 2 /2 inches, and for the curve 30 thedistance was 5 inches. The fan, of course, protruded forwardly from theedge 18 the same distance for all three curves, i. e. one-third of thefan extended forwardly of the edge 18.

a It will be noted that the curve 29 is superior from the standpoint ofair delivered to the curve 28 at all points. In other words, no matterwhat the static pressure is picked out, the fan is handling more airwhen operating on the curve 29 then when operating on the curve 28. The2 /2 inch spacing thus gives better results than the 1% inch spacing.Also, comparing the curve 29 with the curve 30, it will be noted thatfor the lower pressures more air is handled when the distance betweenthe forward end of the shroud and the panel is 5 inches. However, forthe greater pressures, in other words, for pressures above .425 inch ofmercury, the curve 29 is superior; that is, the fan handles more airwhen the distance between the front end of the shroud and the panel isonly 2 /2 inches. Since the purpose of my fan arrangement is to maintainflow even when rather high pressures are required, as when the airtreating means such as the filter 4 clog up, I therefore consider thecurve 29 to be the superior performance curve of the three curvesillustrated. 7

It is also to be noted that when the distance between the forward edgeof the shroud and the panel is 2 /2 inches, which distance gives thebest results for a ten inch fan, the annular peripheral area between thepanel and the forward edge of the shroud for a ten inch fan isapproximately equal to the area of the'intake opening to the fan definedby the shroud. The minimum diameter of the shroud is about 10%; inchesfora ten inch-fan, and it thus defines an intake opening ofapproximately 78.5 square inches. With a 2% inch spacing between thepanel and the front of the shroud, the annular peripheral areatherebetween is also approximately equal to that figure. Moreover, thisrelationship of the most desirable results being obtained when theintake area equals the peripheral discharge area tends to hold true asthe size of the fan is changed. Specifically, I have tested variousfans, eight inches in diameter and larger, and have found that the bestperformance is obtained from all of these fans when the intake area tothe fan defined by the shroud is approximately equal to the annularperipheral area between the front edge of the shroud and the panel.Also, this relationship holds true regardless of the pitch of theblades. Even though changing the pitch changes the results obtained, thebest results still occur when the area of the intake opening equals thearea of the peripheral discharge opening.

Returning to the ten inch fan of the curves (Fig. 3), as the distancebetween the panel and the shroud increases beyond 5 inches theperformance of the fan steadily moves away from my improved pressure andvolume effect and toward the normal performance characteristics of a teninch fan. In other words, the performance steadily moves from the moreor less inclined high pressure characteristic of curve 30 toward therelatively level, normal, low pressure characteristic defined by curve27. This same sort of change also tends to occur for other sizes offans. Thus ordinarily for good results from my fan arrangement, theannular peripheral area between the shroud and the front panel shouldnot be more than 200% of the intake area to the fan. Conversely, forgood results, I would not decrease the aforesaid peripheral area betweenthe front of the shroud and the panel to less than 50% of the intakearea to the fan. Below that point there tends to be choking or retardingof the flow so that although it is still possible to produceconsiderable pressure, nonetheless the flow rate is materiallydecreased. Of course, it is possible to obtain my increased pressureeffect when the distance between the shroud and the panel is beyondthese limits. But ordinarily to obtain desirable results the annularperipheral area between the front of the shroud and the panel should befrom 50% to 200% of the intake area to the fan defined by the shroud.

Referring now to Fig. 4 I have shown therein the effects which areobtained when the distance between the sides 20 and 21 is varied. As inFig. 3 the curve 27 is included to show the normal performance of thefan when my novel fan arrangement is not used, in other words, when thefan is blowing freely and directly out into the room without a radiallydiverting panel and collecting chamber. The remaining curves 31, 32, 33and 34 in Fig. 4 show different performance characteristics which areobtained from the fan 11 for different distances between the sides 20and 21 of the chamber. As mentioned above, these curves are made with aten inch fan driven by a ,3 horsepower motor as approximately 1550revolutions per minute. To take the curves, the bottom wall 16 wasspaced 2 inches from the fan periphery, and the fan and the shroud werefixedly positioned so that the forward edge 18 of the shroud was spaced2 /2 inches from the panel 23. The curve 31 shows the performance of thefan when the sides of the chamber are spaced 12 inches apart, the curve32 when the sides are spaced 14 inches apart, the curve 33 when thesides are spaced 16 inches apart, and the curve 34 when the sides arespaced 18 inches apart. The curve 34 taken on the 18 inch spacing is thebest curve i. e. for any given pressure the fan maintains the greatestflow when operating on it. All of the curves are however obviouslysuperior in pressure to the normal curve 27.

When the sides are spaced beyond 18 inches for this size fan, the fanperformance thereupon begins to steadily approach the normal performancecurve 27. Some, and eventually all, of the desirable effects of myarrangement are lost as the distance between the sides is increasedbeyond 18 inches. When the sides are spaced 18 inches apart, thedistance between the periphery of the blades and the sides of thechamber is approximately 4 inches or less than 50% of the diameter ofthe ten inch fan. In other words, with the ten inch fan the best resultsare obtained when the sides of the chamber are spaced a distance fromthe periphery of the fan which is less than 50% of the diameter of thefan. Further, I have found from many tests made of fans eight inches indiameter and larger, that this relationship holds true with fans ofvarious size, within wide limits. It will be understood, of course, thatmy novel fan arrangement can be used with the chamber sides spacedbeyond this 50% limit, but the desirability of the performance obtainedordinarily decreases as the sides are moved beyond it. Also there is alimit on the minimum spacing of the side walls from the periphery of thefan for good results. I have found the allowable minimum spacing isabout of the diameter of the fan. If the side walls are brought closerto fan periphery than that, my increased pressure and volume effect isprogressively lost.

It will be noted that the side walls 20 and 21 are spaced equidistantfrom the sides of the fan. I have found that substantially equidistantspacing is necessary for the effective operation of my new and improvedfan arrangement, and that the best results are obtained if the innersurfaces of the side walls are parallel. If one side is spaced from theperiphery of the fan a distance substantially greater than the otherside, a portion of my increased pressure and volume effect is lost. Infact if the difference in spacing is great enough, the entire increasedpressure and volume is lost. When the sides are not spaced substantiallyequidistant, the air is able to escape on the side spaced further fromthe fan without any considerable interference and thereby there is nodecrease in velocity and rise in pressure.

Further, the spacing of the bottom wall 16 is also important to theoperation of my fan arrangement. For

best results its spacing from the periphery of the fan should be equalto that of the sides of the chamber; and in any case it should be spacedfrom the fan periphery a distance not greater than 50% of the diameterof the fan. A greater spacing than that results in the increasedpressure and volume effect being decreased, and if the spacing is madelarge enough, the effect is entirely lost. In taking the curves shown inFigs. 3 and 4 the bottom wall was of course spaced nearer to the fanthan were the side walls but this was done only to decrease the size ofthe apparatus and some of my increase pressure and volume effect waslost as a result. In this particular application, however, the advantageof space saving outweighed the slight decrease in performance. Like thesidewalls the bottom wall should not be spaced closer to the peripheryof the fan than 10% of the diameter of the fan.

Referring now to Fig. 5 I have shown therein a second embodiment of mynew and improved fan arrangement. This fan arrangement is mounted withinan air purifier or filtering appliance 40. The air purifier 40 includesan outer housing or casing 41 to which an inlet opening is defined atthe rear thereof. A filtering element 42 is positioned in front of thisopening so that any air flowing into the unit passes through the filterand is filtered thereby. This filter may be either of the electrostaticor the mechanical type or may be a combination of both. After flowinginto the filter 42 the intake air enters a chamber 43 positioned behinda fan. 44.

The fan 44 is of the conventional axial flow propeller type and isincorporated in an alternate embodiment of my new and improved fanarrangement. As shown, the fan 44 is driven by means of an electricmotor 45 and the mounting for the fan and the motor is provided bysuitable mounting brackets 46 which are attached to the casing 41. Theintake opening to the fan is formed by means of a scroll 47 whichsurrounds at least the rear portion of the blades and preferablytwo-thirds thereof from rear to front; and this scroll 47 is eitherattached to or formed integrally with the wall 48 which serves as thefront wall of the chamber 43 behind the fan. In accordance with myinvention, the output flow from the fan is blown directly against apanel 49 which comprises the front wall of the housing 41. The panel 49is positioned directly in front. of the fan and it diverts the outputflow radially outward into a chamber 50 defined by the panel itself,theside walls of the housing (not shown), the scroll'47, the wall 48, andthe bottom wall 50a of the housing. This chamber 50 contains a body offree air in which the flow is then collected, and it preferably includesright angleor square bottom corners to damp any whirling circulationtherein.

Due to the action set up by the panel 49 and the chamber 50 a pressurerise is effected in the output of the fan 44 in the same manner as waseffected for the fan 11 of the embodiment of Figs. 1 and 2. Afterexperiencing this pressure rise the output flow of the fan is thendischarged through -an outlet 51 in the top wall of the chamber. Thisopening 51 may be covered by any suitable means, as for example by aperforate grill, to pre: vent anyone from sticking his hand or droppingobjects down into the fan.

. The foregoing structure is essentially the same as shown in Figs; 1and 2, but in the embodiment ofFig. 5 I have provided additional meanswhich reduce the noise of the fan and which also tend to improve theperformance characteristics somewhat. These additional means comprise amember 52 which is mounted on the shaft 53 of the fan between the fanand the panel 49. This member 52, which preferably comprises a circulardisk, rotates at the same speed as the fan and helps the wall 49 indiverting the axial flow from the fan radially outward. The disk 52 ineffect reduces friction by allowing the air leaving the fan to slip offradially from a moving member rather than being diverted by a stationarymember.

As mentioned above, this not only decreases noise but also improves theperformance characteristics of the fan arrangement somewhat. This diskmay be made of any suitable material as, for example, aluminum. Althoughthe size of the disk may be varied I have found that the preferable sizeis approximately four-fifths that of the fan. Thus, if a ten inch fan isused, the disk for best results should be approximately eight inches indiameter.

It will be understood that the fan arrangement of Fig. operates to pullair through its filter in the same manner as does the fan arrangement ofFig. 1. In other words, the fan arrangement of Fig. 5 creates a vacuumin the chamber 43 behind the filter so that atmospheric pressure forcesair through the filter, and then it raises the air to a pressuresomewhat above atmospheric in the chamber 50 so that the airfiowsoutwardly into the room.

Referring now to Fig. 6, I have shown therein another embodiment of myinvention. This embodiment comprises an air purifying or filteringappliance 60 which incorporates a still different modification of my newand improved fan arrangement. This air filtering appliance 60 includes ahousing 61 to which an inlet opening 62 is formed in one wall thereof.Communicating directly with this inlet opening is a shroud 63 whichdefines an intake opening to an axial flow propeller fan 64. The shroud63 is so designed that it surrounds at least the rear or intake portionof the fan 64, and in my preferred arrangement it surroundsapproximately two-thirds of the fan from its intake to its outlet side.The fan 64 itself is driven from a suitable electric motor 65 by meansof a shaft '66. The mounting for both the fan and the motor isaccomplished by means of a plurality of brackets 67 which are securedtothe casing of the motor and to the housing 61.

In accordance with my invention the fan 64 is so arranged that apressure rise is effected in the output flow thereof. This pressure risein the output flow enables the fan 64 to force the air taken in throughthe shroud 63 out through a filter element 68 which is positioned overthe outlet opening from the housing 61. Specifically, the outlet openingand the filter element extend completely across the top area of thehousing 61.

In order to effect a pressure rise between the fan 64 and the filterelement 68 a panel 69 is positioned directly in front of the output sideof the fan. The panel 69 diverts the axial output flow of the fanradially outward in all directions. This radial output flow is thencollected in a chamber 70 which surrounds the fan 64 and the scroll 63.The chamber 70, which is defined by the panel 69, the bottom plate 71 ofthe housing, the scroll 63, an extension 71a of the panel 69, and theside walls of the housing (not shown), contains abody of free air andthis free air slows down and collects the radial output fiow as it movesoutwardly into the chamber. As a result a pressure rise occurs in theoutput flow in the same manner as described With respect to theembodiment of Figs. 1 and 2. After so increasing in pressure the airthen passes outwardly through the filtering element 68.

To improve further the results obtained from the fan arrangement, arotating disk 72 is mounted on the same shaft as the fan 64 between thefan and the panel 69. This disk 72 materially reduces the friction asthe air is diverted from the axial direction to a radial flow andthereby both reduces noise and improvesthe performance characteristics.The size of the disk may be varied, but preferably its diameter shouldbe four-fifths that of the fan.

In this embodiment of my invention, the new and improved fan arrangementoperates to create a high pressure behind the filter rather than tocreate a partial vacuum between the filter and the intake of the fan.Here the fan takes in atmospheric air and then through my improved fanarrangement, a high pressure is created as the fiow moves radiallyoutward into the chamber 70. This high pressure in turn forces the .airout through the filter 68 and enables a substantial flow to'bemaintainedeven upon some clogging of the filter. It will be understood that thefilter 68 can be either an electrostatic filter or a mechanical filteror a combination of both. Itwill also be noted that the space 73directly behind the filter 68 is made considerably Wider than the otherportions of the collecting chamber 70. This permits the use of a filterof large area. The other portions of the chamber 70, of course,communicate directly with this space 73. As in the previously describedembodiments, the bottom corners of the collecting chamber are preferablyformed as right-angle or square corners thereby to damp any whirlingflow in the. chamber.

Referring now to Figs. 7 and 81 have shown therein still anotherembodiment of my invention. This embodiment comprises an air purifyingappliance which in corporates another modification of my new andimproved fan arrangement. The appliance 80 includes a housing 81 towhich an inlet opening is defined at the rear end thereof. A filterelement 82 is positioned over this opening so that any air flowingthrough the opening must pass therethrough; and in order to set up aflow of air through the opening and the filter, an axial fiow propellerfan 83 is mounted within the housing 81. The fan 83 is driven by a motor84 by means of a shaft 85, and both fan 83 and the motor 84 are mountedby means of a plurality of bracket members 86 which are firmly attachedto the casing of the motor and to the housing 81. The intake opening tothe fan 83 is defined by means of a shroud 87 which communicates withthejspace88 lying between the filter element 82 and the fan. The shroud87, which is an annular member, surroundsat least the rear portion ofthe fan in order to form the intake opening and preferably it extendsforwardly a distance along the periphery of the fan. For best results Ihave found that it should extend for two-thirds of the distance fromtherear to the front of the fan.

In order that the fan 83 may create the desired flow of air through thefilter 82, I have provided means which together with the fan compriseanother modification of my new and improved fan arrangement. This meansincludes a panel 89 which is positioned directly in front of the fan 83,and a collecting chamber 90 which surrounds the fan and the shroud 87.In this arrangement, the axial output fiow from the fan flows directlyagainst the panel or plate 89 and is diverted radially thereby. Theradial flow then moves outwardly into the chamber 90 surroundingthescroll 87 and the fan and is slowed down and collected in a body of freeair lying in this chamber. The chamber 90 includes the panel 89 as thefront wall thereof and the scroll 87 as a portion of the rear wallthereof. The side walls (not shown) of the housing form the sides of thechamber 90, and the top and bottom walls of the chamber are formed bywall members 91 and 92 which are attached to or formed integrally withthe scroll. The corners of the chamber are preferably formed asright-angle or square corners to damp any whirling flow in the chamber.

For the reasons discussed with respect to the embodiment of Figs. 1 and2 the output flow from the fan 83 increases in pressure as it isdiverted radially outward and collected in the chamber 90. In thisembodiment the increased pressure airis however discharged from thecollecting chamber in adifferent manner than it was from the collectingchamber ofFigs. l and 2. Specifically in Figs. 7 and 8 the'dischargeopening from the chamber 90 comprises a continuous aperture 93 whichextends around the plate 89. The discharge flow thus leaves the chamber90 flowing in essentially the same axial direction as it was beforebeing diverted radially by the plate 89. The plate 89 is of sufiicientsize though that an increased pressure efiect is created in the flowbefore it reaches the discharge opening. The inner sides ofthe aperture93, i. e., the outer edges of the plate 89, are spaced outwardly fromthe periphery of the fan 83 and the scroll 87 so that the air is bothdiverted radially and slowed down and collected in a body of free'airbefore it reaches the aperture 93. These two actions, as in the otherembodiments, cause an increase in pressure in the flow between the fanand the discharge opening.

In the embodiment of Figs. 7 and 8, the fan arrangement creates a fiowthrough the filter 82 by creating a partial vacuum in the space 88behind the filter. Atmospheric pressure thus forces air through thefilter. The air then passes through the fan 83 and is raised in pressureas it flows outwardly radially outward into the chamber 90. After risingto a pressure somewhat above atmospheric the air is finally dischargedoutwardly through the opening 93 into the room.

Although I have not shown performance curves for the embodiments ofFigs. -8 it will be understood that they produce results equivalent toor better than the results shown in Figs. 3 and 4 for the embodiment ofFigs. 1 and 2. In fact, as mentioned above, the inclusion of a rotatingdisk between the fan and the radially diverting panel, as shown in Figs.5 and 6, both reduces noise and improves the output characteristics ofthe fan arrangement somewhat. The rotating disk can also be included inthe embodiment of Figs. 7 and 8 and in fact, if desired, the panel 89could be replaced by a rotating disk or somewhat larger diameter thanthe fan 83. In the latter case the disk in effect becomes a wall of thecollecting chamber. Thus when I state that the chamber includes thepanel placed in front of the fan, it will be understood that the panelmay be fixed to it, or the panel may be rotatingwith respect to it.Further, although in the various illustrated embodiments I have shownthe discharge opening from the collecting chamber as leading eitherthrough the top or the front of the chamber, my invention is not limitedto embodiments wherein the opening is in such walls. Rather the openingfrom the collecting chamber could be in the bottom of the chamber or ifsuitable passageways are pro vided the opening could lead therefrom backthrough the same wall in which the inlet to the fan is taken. Of course,with this latter arrangement suitable bathe means would have to beprovided between the inlet and the outlet in order to separate theintake and discharge fiows.

It should be noted incidentally that the same dimensional relationshipsmentioned with regard to the embodiment of Figs. 1 and 2 also apply tothe embodiments of Figs. 58. For the best operation the spacing of theflow diverting panel from the forward edge of the shroud, and thespacing of the side walls and the bottom wall of the collecting chamberfrom the periphery of the fan should be generally the same in Figs. 58as in Figs. 1 and 2. In these embodiments also, the pcripheral dischargearea between the forward end of the shroud and the panel shouldpreferably be from 50% to 200% of the intake area to the fan defined bythe shroud; and the side walls and the bottom Wall of the collectingmember should preferably be spaced from the periphery of the fan adistance less than 50% but greater than of the diameter of the fan.Further,,the spacing of the side walls from the fan should be the same,e. g. they should be equidistant therefrom, and preferably the spacingof the bottom of the chamber from the fan should also be the same asthat of the side walls. Moreover, in Figs. 7 and 8 the same spacing ispreferably used for the top of the chamber also.

Referring now to Figs. 9 and 10 I have shown therein still anothermodification of my improved fan arrangement. This embodiment includes acasing 101 to which an inlet opening is defined at the rear thereof. Amechanical or electrostatic filter (not shown) may be positioned infront of this inlet so that any air passing through the casing 101 isfiltered or purified.

In order to set up a flow of air through the casing 101 there is mountedtherein a generally axial fiow propeller 102. This fan is mounted in thesame manner as the fan of the embodiment ofFigs. 1 and 2 and is drivenby a suitable electrical motor (not shown). The intake opening to thefan 102 is defined by means of an annular shroud 103 which communicateswith the space 104 lying behind the fan. The shroud 103 surrounds atleast the rear portion of the fan in order to form the intake openingand preferably it extends forwardly a distance along the periphery ofthe fan. As in the previously discussed embodiments the best results areobtained when it extends forwardly for two-thirds of the distance fromthe rear to the'frorit of the fan.

In accordance with my invention the output from the fan 102 flowsdirectly against a panel or plate 105 positioned in front of the fan,and is diverted radially by this plate. The radial flow then movesoutward into a chamber 106 surrounding the scroll and the fan and isslowed down and collected in a body of free air lying in this chamber.The chamber 106 includes the panel 105 as the front wall thereof and thescroll 103 as a portion of the rear wall thereof. The side walls andbottom walls of the chamber are not shown but it will be understood thatthe chamber is similar to the chamber shown in the embodiment of Figs. 1and 2. Like the chamber of that embodiment, it preferably includessquare or right-angle corners at its bottom.

For the reasons described at length with regard to the otherembodiments, the output flow from the fan 102 increases in'pressure asit is diverted outwardly and collected in the chamber 106. In thisembodiment, however, a somewhat different means is provided fordischarging the air from the chamber. In this embodiment the outletopening from the chamber is comprised of 'a plurality of slots 107 whichare defined in a cover member 108 mounted at the top of the chamber 106.The number and size of the slots 107 are such that the discharge fromthe chamber1106 is somewhat restricted, and as a result a pressure isbuilt up within the chamber 106. Further, the slots 107 are so shapednarrowing from their inlet sides to their outlet sides that they form oract as nozzles. Acting as nozzles the slots 107 are effective toincrease the velocity of the air as it is discharged therethrough; andalong with this increase in velocity a cooling of the air also occurs.Due to the pressure-volume change effected by the slots the temperatureof the air decreases as it is accelerated. The higher the accelerationof the air, the cooler the air becomes. The provision of the slots 107thus results in a rapidly moving cool stream of air being dischargedfrom the casing 101.

The cover 108 and the slots 107 are so arrange-d that the air isdischarged in an upward direction toward the ceiling of the room inwhich the casing or appliance 101 is positioned. Moreover, the slots areso arranged that the discharge air is confined or shaped to a narrowstream of relatively small proportions until it reaches the upper levelof the room. At this upper level the high velocity air is then sloweddown by the resistance of the free air in the room. After slowing down,the air spreads out and because of its coolness settles gently in adownward direction. By this method the air is introduced into the roomwithout the annoyance of an air stream blowing directly onto any personwithin the room. This embodiment of my fan arrangement is thus efiectiveto produce a particularly pleasing result, since it discharges a coolstream of air which due to its velocity and direction of dischargecirculates throughout the room but yet does not blow directly on theuser. Additionally, if this fan arrangement is placed in a window sothat it draws in outside air through its intake, it is effective toproduce a higher degree of cooling than can be obtained from aconventional fan placed in a window. The effect produced by the slots107 results in a cooler stream of air being introduced into the room.

It will be understood that the same dimensional relationship discussedwith respect to Figs. 1 and 2 also applies to this embodiment of my fanarrangement. Here again, for best results the peripheral discharge areabetween the forward end of the shroud and the panel should preferably befrom fifty percent to two hundred percent of the intake area to the fandefined by the shroud; and the side walls and the bottom wall of thecollecting chamber should preferably be spaced from the periphery of thefan a distance not less than 50% but more than of the diameter of thefan. Further, the side walls should bespaced equidistant from the fanand, preferably the same spacing should also be used for the bottomwall. Also, a rotating disk may be mounted between the fan 102 and thepanel 105 in order to reduce noise and improve the outputcharacteristics of the fan arrangement somewhat.

It will be noted that in this embodiment, as in the embodiment of Figs.1 and 2, the collecting chamber widens out from front to rear just belowthe outlet. Such a widening was, of course, not necessary in theembodiment of Figs. 1 and 2, but here it is desirable in order that asufiicient number of slots 107 may. be provided to handle the flow andmaintainv the desired characteristics therein.

. While in accordance with the patent statutes I have described. what atpresent are consideredto be the preferred embodiments of my invention,it will be obvious to those skilled in the art that various changes andmodifications maybe made therein and I, therefore, aim in the appendedclaims to cover all such changes and modifications as fall within thetrue spirit and scope of my invention.

I claim:

1. A fan arrangement comprising a generally axial flow fan having aplurality of blades, an annular shroud forming an intake opening to saidfan and surrounding only the upstream portion of said fan, and means foreffecting a pressure rise in the output flow from said fan, said meansincluding a planar baifie positioned substantially at right angles tothe axis of said fan in front of the output side of said fan fordiverting radially the axial flow therefrom, the annular peripheral areabetween said panel and the forward edge of said shroud being from 50% to200% of the area of said intake opening to said fan defined by saidshroud, a rectangular shaped chamber surrounding at least the forwardportions of said fan and said shroud and containing a body of freeair-for collecting therein the radial flow effected by said planarbafHe, said rectangular shaped chamber having three side walls spacedsubstantially equidistant from 16 said fan and enclosing the peripheryof said fan around at least three sides thereof, and means defining anair outlet opening in the fourth side Wall of said chamber outwardly ofthe periphery of said blades.

2. A fan arrangement comprising a generally axial flow fan having aplurality of blades, an annular shroud forming an intake opening to saidfan and surrounding only the upstream portion of said fan, and means foreffecting a pressure rise in the output flow from said fan, said meansincludinga planar baffle positioned substantially at right angles to theaxis of said fan in front of the output side of said fan for divertingradially the axial output flow therefrom, the annular peripheral areabetween said planar baffle and the forward edge of said shroud beingfrom 50% to 200% of the area of said intake opening to said fan definedby said shroud, a rectangular shaped chamber surrounding at least theforward portions of said fan and said shroud and containing a body offree air for collecting therein the radial flow effected by said planarbafile, said rectangular shaped chamber including said shroud as aportion of the walls thereof and having side walls spaced from theperiphery of said fan a distance less than 50% of the diameter of saidfan and enclosing the periphery of said fan around at least three sidesthereof, said chamber having generally square corners at the enclosedend thereof for damping circulating fiow within said chamber, .and meansdefining an air outlet opening from said chamber at the end thereofopposite from said end with square corners.-

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